Currently I own Alto k10 CNG, however I have driven new Wagon R of my friend and I loved it. I am considering to upgrade next year. Due to my high usage I prefer CNG cars. So far Alto k10 is serving me flawlessly for last 4 years. Considering the same 1 liter engine with new version I'm sure it's going to be reliable.
Best part is it's frugal as well as it has enough power. I never felt any loss of power on highways.
I considered I10 nios & Aura CNG versions but I will have to stretch my budget by almost 3 lakhs. Which isn't feasible as Wagon R has good space on offer, comfy seats, rear AC vents, good interior, great mileage & great service backup. It ticks all the boxes considering my small family of 4 people.